Polypyrrole-boosted photothermal energy storage in MOF-based phase change materials

Infiltrating phase change materials (PCMs) into nanoporous metal–organic frameworks (MOFs) is accepted as a cutting-edge thermal energy storage concept. However, weak photon capture capability of pristine MOF-based composite PCMs is a stumbling block in solar energy utilization. Towards this goal, we prepared advanced high-performance pristine MOF-based photothermal composite PCMs by simultaneously integrating photon absorber guest (polypyrrole [PPy]) and thermal storage guest (1-octadecanol [ODA]) into an MOF host (Cr-MIL-101-NH₂). The coated PPy layer on the surface of ODA@MOF not only serves as a photon harvester, but also serves as a phonon enhancer. Resultantly, ODA@MOF/PPy composite PCMs exhibit intense and broadband light absorption characteristic in the ultraviolet–visible–near-infrared region, and higher heat transfer ability than ODA@MOF. Importantly, the photothermal conversion and storage efficiency of ODA@MOF/PPy-6% is up to 88.3%. Additionally, our developed MOF-based photothermal composite PCMs also exhibit long-standing antileakage stability, energy storage stability, and photothermal conversion stability. The proposed coating strategy and in-depth understanding mechanism are expected to facilitate the development of high-efficiency MOF-based photothermal composite PCMs in solar energy utilization.